1. Field of the Invention
This invention relates in general to a heat dissipation structure, and in particular to a heat dissipation structure for a heat-dissipating fan unit.
2. Description of Related Art
Conventional heat dissipation structures for box fan units can be generally categorized into two groups. One group of these heat to dissipation structures has plastic frameworks with copper linings. The other group has metallic frameworks made of metals such as aluminum.
Frames for a fan unit with copper lining is low in cost, light in weight and features electrically insulating body, which is advantageous in preventing short-circuiting in the environment of printed circuit boards (PCB). However, its plastic frame is also thermally insulating that the heat generated by the fan rotor bearing accumulates. This is because the copper lining is totally enclosed by the plastic. This heat accumulation in the fan motor increases the motor operating temperature and reduces the motor life expectancy. Thus, copper lining plastic fans are only suitable for applications with slow fan speeds and low fan motor power ratings. This prevents damage to the fan motor as low-power and slow-speed motor operation allows to keep the motor operating temperature reasonably low. Due to this power and speed limitation, copper lining plastic fans are limited in their possible applications.
To overcome this limitation, metallic materials such as aluminum or its alloy is used to construct the framework for heat dissipation fans. A metal frame for heat dissipation fans is efficient in thermal conduction, it is capable of effectively dissipating heat generated in the fan motor, including heat generated in the motor bearing. A fan motor can thus be maintained at low operating temperature, which allows the fanned heat dissipation unit to enjoy its life expectancy. However, a metallic frame for these fanned heat dissipation units costs relatively higher and is commercially less competitive than its plastic counterpart. Meanwhile, in addition to being weighting much heavier, a metallic frame is also potentially dangerous in the PCB environment as it may cause short-circuiting among the components of the PCB since it is itself electrically conductive.